The spatial resolution of a conventional Brillouin Optical Time-Domain Analysis (BOTDA) distributed sensor system is generally limited by a combination of linewidth broadening and reduced signal strength associated with the use of short optical pulses [See Fellay, A., Thévenaz, L., Facchini, M., Niklès, M., and Robert, P., “Distributed sensing using stimulated Brillouin scattering: towards ultimate resolution”, OFS'96, pp. 324-327, 1996 and Bao, X., Brown, A., DeMerchant, M., and Smith, J., “Characterization of the Brillouin-loss spectrum of single-mode fibers by use of very short (<10-ns) pulses”, Optics Letters, Vol. 24, No. 8, pp. 510-512, 1999]. Maximum spatial resolutions of 1 m are typical of such systems, although some progress has been made toward further enhancements [See Bao, X., Brown, A., DeMerchant, M., and Smith, J., “Characterization of the Brillouin-loss spectrum of single-mode fibers by use of very short (<10-ns) pulses”, Optics Letters, Vol. 24, No. 8, pp. 510-512, 1999.; Brown, A. W., DeMerchant, M. D., Bao, X., and Bremner, T. W., “Spatial resolution enhancement of a Brillouin-distributed sensor using a novel signal processing method”, Journal of Lightwave Technology, Vol. 17, No. 7, pp. 1179-1183, 1999 and Brown, A. W., Smith, J. P., Bao, X., DeMerchant, M. D., and Bremner, T. W., “Brillouin scattering based distributed sensors for structural applications”, Journal of Intelligent Materials Systems and Structures, Vol. 10, pp. 340-349, 1999.] with a resolution in the 500 to 100 mm range having been reported.
For this reason, other methods such as frequency-domain reflectometry [See Garus, D., Gogolla, T., Krebber, K., and Schliep, F., “Brillouin optical-fiber frequency-domain analysis for distributed temperature and strain measurements”, Journal of Lightwave Technology, Vol. 15, No. 4, pp. 654-662, 1997] and correlation-based methods [See Hotate, K., and Tanaka, M., “Distributed fiber Brillouin strain sensing with 1-cm spatial resolution by correlation-based continuous-wave technique”, IEEE Photonics Technology Letters, Vol. 14, No. 2, pp. 179-181, 2002] have been proposed to obtain higher resolution. In both cases, however, improved resolution has come at the cost of acquisition speed and/or overall sensing length. There is a need, therefore, for a system and method of obtaining centimeter resolution from a time-domain pump and probe configuration that does not compromise acquisition speed or sensing length.